Category

Published on

08 Oct 2008

Abstract

Functionally graded materials (FGM’s) are designed to achieve levels of performance superior to that of homogeneous materials by combining the desirable properties of each constituent phase. FGM’s are composite materials where the composition or the microstructure is locally varied so that a certain variation of the local material properties is achieved.

The technology of Functionally Graded Materials was an original material fabrication technology proposed in Japan in 1984 by Sendai Group. The interest in graded materials focused primarily on the control of thermal stresses in elements exposed to high temperatures (to 1600 ºC), for instance in gas turbine blades, aerospace structures, solid-oxide fuel cells, energy conversion systems using thermoelectric or thermionic materials (thermal barrier coatings-TBC). Subsequent applications include fusion and fast-breeder reactors as a first-wall composite material, piezoelectric and thermoelectric devices, high density magnetic recording media, in optical applications as graded refractive index materials in audio-video discs, in bioengineering as dental and orthopaedic implants, in structures as fire retardant doors and penetration resistant materials for armour plates and bullet-proof vests.

FGM concepts were also applied to thin coatings and nanomaterials fields. With the development of thin films technology in various areas of materials science, the potential use of novel surfaces and more reliable coating materials by employing nanocomposite and layered-graded thin films in mechanical, tribological, optics, energy, bio-implants applications among others can be considered.

Nanostructured materials and graded and layered thin films offer the potential for significant improvements in nano-engineering and opto-electronic properties based on improvements in physical, chemical and nanomechanical properties resulting from reducing microstructural features by decreasing the grain size of a material to the nanometer range compared to current technological materials.

In this presentation it will be presented an overview of the FGM approaches to produce novel nanostructured materials, in particular, for solar energy applications. Topics to be discussed include introduction to FGM thick coatings concepts, from functional composite and graded coatings to nanograded thin films used in solar energy, produced by clean PVD technologies (Physical Vapour Deposition) and other deposition techniques.